Biomechanical comparison between double-plate fixation and posterior plate fixation for comminuted olecranon fracture using two triceps screws in synthetic bone model

Abstract

Background: Although preventing triceps fragment displacement is essential for treating an olecranon fracture, we frequently encounter situations in which only a few screws can be fixed to the triceps fragment. The aim of this study was to compare the stability of double-plate fixation and posterior plate fixation for olecranon fractures when the triceps fragment was small and only 2 screws could be inserted. Methods: A composite ulna model was used to simulate olecranon fracture. Four groups were formed consisting of double-plate and posterior plates with cortical and locking screws. The cyclic loading test was conducted for 500 cyclic loads of 5 to 50 N on a specimen to measure micromotion and displacement of the gap caused by light exercise. The load-to-failure test was performed by applying a load until fixation loss, defined as when the fracture gap increased by 2 mm or more or catastrophic failure occurred, to measure the maximum load. Results: Eight samples per group were tested through the pilot study. All groups were stable with a micromotion of <0.5 mm. However, the mean micromotion showed significant differences between the 4 groups (P < .001, Table 1). In the mean micromotion during exercise, posterior plating with cortical screws was the most stable (0.09 ± 0.02 mm) while double-plating with cortical screws was the most unstable (0.42 ± 0.11 mm). At the maximum load, posterior plating with locking screws was the strongest (205.3 ± 2.8 N) while double-plating with cortical screws was the weakest (143.3 ± 27.1 N). There was no significant difference in displacement after light exercise between the groups. Conclusions: This study showed that when 2 triceps screws were used, both groups were stable during light exercise, but posterior-plating was stronger than double-plating.